Do i need to connect my arduino uno ground while having an external power ?

Using Arduino General Electronics
#1

Hi,

Sorry i certainly a stupid question but i like to make sure i do thing in the right way.

I have some component in a breadboard that use a lot of power ( more than what my arduino can provide ). So i have an external power connected to the breadboard. The Atmega is still on the arduino board and i am using digital pin to communicate with the component on the breadboard. Do i need to connect the GND pin of my arduino to the GND on the breadboard ? ( which is connected to an external power) . I am doing that right now because i thought it was correct ( not sure) but i like to know the why.
Thanks in advance

All the best

Vincent

#2

Always connect the grounds together. Among other things, the ground connection defines zero for the signal levels on Arduino pins.

#3

Thanks a lot

#4

If you are unsure about the GND, think of a simple battery (cell)

If you connect only the positive end to your circuit, what happens? That's right, absolutely nothing.

The key word here is "Electronic Circuit" - it needs to be a closed 'circuit' for current to flow.

With the exception on radio transmission, you always need the ground.

#5

See this:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html

#6